For \(QQ\bar{q}\bar{q}\) , it is known for decades that in a static and flavor-independent potential, the system becomes bound if the mass ratio \(M/m\)  is large enough. Moreover, in the case of \(QQ\bar{u}\bar{d}\)  with isospin \(I=0\)  , the binding is favored by the chromomagnetic interaction. See, e.g., [1]}, and the recent discussion about various dynamical effects [2]}.
